Question: Where we can use subquery in SQL?

WHERE subquery can be used?

Subqueries can be used with SELECT, UPDATE, INSERT, DELETE statements along with expression operator. It could be equality operator or comparison operator such as =, >, =, <= and Like operator. A subquery is a query within another query. The outer query is called as main query and inner query is called as subquery.

What is a subquery when is it used?

A Subquery or Inner query or a Nested query is a query within another SQL query and embedded within the WHERE clause. A subquery is used to return data that will be used in the main query as a condition to further restrict the data to be retrieved.

What is subquery in SQL with examples?

A subquery is a query that is nested inside a SELECT , INSERT , UPDATE , or DELETE statement, or inside another subquery. … A subquery can be used anywhere an expression is allowed. In this example a subquery is used as a column expression named MaxUnitPrice in a SELECT statement.

Which is faster joins or subqueries?

The advantage of a join includes that it executes faster. The retrieval time of the query using joins almost always will be faster than that of a subquery. By using joins, you can maximize the calculation burden on the database i.e., instead of multiple queries using one join query.

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Why subquery is used in SQL?

An SQL subquery is a query inside another query. It is used in the WHERE or HAVING clause of an SQL statement. Subqueries let you specify the results of one query as an argument in another query. When you’re writing an SQL query, you may want to specify a parameter based on the result of another query.

Does not exist SQL?

The SQL NOT EXISTS Operator will act quite opposite to EXISTS Operator. It is used to restrict the number of rows returned by the SELECT Statement. The NOT EXISTS in SQL Server will check the Subquery for rows existence, and if there are no rows then it will return TRUE, otherwise FALSE.

What is pivoting in SQL?

Pivot and Unpivot in SQL are two relational operators that are used to convert a table expression into another. Pivot in SQL is used when we want to transfer data from row level to column level and Unpivot in SQL is used when we want to convert data from column level to row level. … You may use your own database tables.

Which SQL keyword is used to retrieve a maximum value?

MAX() is the SQL keyword is used to retrieve the maximum value in the selected column.

What are the types of subquery?

Types of SQL Subqueries

  • Single Row Subquery. Returns zero or one row in results.
  • Multiple Row Subquery. Returns one or more rows in results.
  • Multiple Column Subqueries. Returns one or more columns.
  • Correlated Subqueries. …
  • Nested Subqueries.
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What is query in SQL?

What Does Query Mean? A query is a request for data or information from a database table or combination of tables. This data may be generated as results returned by Structured Query Language (SQL) or as pictorials, graphs or complex results, e.g., trend analyses from data-mining tools.

What is difference between join and subquery?

Joins versus Subqueries. Joins and subqueries are both used to combine data from different tables into a single result. … Subqueries can be used to return either a scalar (single) value or a row set; whereas, joins are used to return rows. A common use for a subquery may be to calculate a summary value for use in a query …

How can we insert data into a view?

You can insert rows into a view only if the view is modifiable and contains no derived columns. The reason for the second restriction is that an inserted row must provide values for all columns, but the database server cannot tell how to distribute an inserted value through an expression.

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